Muffler



A118- 16, 1950 L. M. MoRRlsH ETAL 2,949,165

MUFFLER Filed Nov. 26, 1954 INVENTOR B iwf/fe LITTPA/EV ini l .expansion chamber means for rev United States Patent() .'MUFFLER .Leonard M. Morrish and Lloyd E. Muller, Flint, Mich., nssignors to"'General Motors Corporation, Detroit,

Mich., a corporation of'pelraware 1 Filed Nov. 26, 1954Ser. No. 471,240

. length to provide a series of resonating chambers that -.may be tuned to wave lengthsv ofr sounds` 'extending throughout a considerablejfrequeny rang?. to provide l Ving Ithe 4vowV of'juid 1n the structure and for attenuatingsound-s'by acoustical .reilectiorn -to provide a simpleme'asily constructed and relatively .rigid structural memberfwhen constructed 'from thin metallic or' other sheet materiali In thedrawings:

Figure l is a longitudinal section-al view through a mufiier embracing'the principles of the invention.

Figure 2 is a cross-sectional view taken substantially in the plane of line 22 on Figure 1, looking in the `direction of the arrows thereon.

Figure 3 is a fragmentary longitudinal sectional view of a louver structure employed in constructing the muflier and as the structure might appear in the plane of line 3--3 on Figure `l.

Figure 4 is a fragmentary cross-sectional view of the louver structure shown by Figure 3 and taken substantially in the plane of line 44 on Figure 3.

The muer embodying the invention may comprise an outer casing 11 including curved side walls 12 and oppositely disposed end walls 13. In the present instance the side walls 12 are formed by inner and outer metallic sheets 14 and 16 respectively, which may be secured together at 17 -in oval or other suitable form. A sheet 18 of fibrous or other suitable material may be employed between the sheets 14 and 16 for sound absorbing and heat insulating purposes. The end walls 13 may be secured to the side walls 12 by seams indicated at 19.

inlet and outlet conduits 21 and 22 respectively are adapted to project into the casing 11 on opposite sides thereof and to terminate within the casing in adjacent and opposed relation. It is considered preferable that the inlet conduit 21 taper in such a way as to expand inwardly Ito decrease the velocity and increase the pressure of the `fluid discharged by the conduit into the casing. The adjacent and opposed ends yof the conduits 21 and 22 are secured in a supporting partition 23 extending -across the casing 11 and in which openings 24 are formed around the tubes 21 and 22 to provide means by which the ends of the tubes on opposite sides of the partition may communicate. Spaced from the ends of the conduits 21 and 22 is a pair of partitions 26 and 27 which also extend across the casing 11 4and which `divide the casing adjacent the inner extremities of the ltubes into an expansion chamber 28. The expansion chamber 28 has an inlet side 29 into which the inlet conduit 21 discharges on one side of the partition 23 ICC and @gonfler side 31 Afronti/hint theouneteonduit 2z j discharges on the opposite side of the partition 23. Be-

yond the partition 26 and extending towardtheinlet end i, of thegcasing 11 isa ,r$0nating charnber 32 which is connectedtotheoutlet Side 31 of the expansion chamber 2,8` by an acoustical coupling 33. Acousticalcoupling 33 is formed byla tube 34k which is connected to a `flanged opening 36 in the partition 26 in axially aligned relation to the outlet tube 22. Between the partition 27 and the outlet end ofthe casing 1,1, isanother pair of partitionsextending across thecasing 11 and through which fthe outlet conduit 2 2 projects. ,The partitions 27, 37

' and 3.8 divide the outlet en d of the casing 11 into resonating chambers 39, 41 dand 42. g The resonating charnber 39 is connected to the inlet side 29 of the` expansion chamber 2S by an acoustical coupling 43. The coupling 43 is formedby atube 44 connected tov aanged opening 46k formed in `the, partition 27 in axially laligned .relation with the inlet conduit 21.

In order -to provide additional resonating chambers and couplings the outlet conduit 22 may be surrounded by a tubej47 that may, extendgthrough one `of the resonating chambers 39 ino the inlet side 29 of .the expansion chamber 28 and into therresonating lchamber 41. The tube. 47 may be ysupported by the partitions 27 vand 37. The outlet conduit 22 may be supported within the tube 47 by expandingsegments of the conduit into contact Awith annular partitions indicated at 48, 49 and 51. Resonating chambers'52'and 5.3 may beformed between partitions and S1 and the conduit'22`and tube 47. The re'sonating' chambers S2 and 53 may be connected to the conduit 22 by acoustical coupling means indicated at 54 and 56 respectively. The acoustical coupling means 54 and S6 may be formed by providing a plurality of spaced openings 55 through the conduit 22 and which may extend substantially throughout the parts of the conduit exposed to the resonating chambers 52 and 53. In the present instance the openings may be formed by forming rows of slits extending longitudinally and transversely of the parts of the conduit 2'?. and between adjacent pairs of which the wall o the conduit may be extruded outwardly to provide louvers indicate-d at 57. Beyond the partition 51 the tube i7 may communicate with the resonating chamber 41 to provide a part of acoustical coupling means S8 between the conduit 22 and the resonating chamber 41. The acoustical coupling means S8 may comprise a plurality of 'the openings S5 formed by the louvers S7 and extending lthroughout the greater part of the conduit 22 disposed within the end of the tube 47 and the annular passage 59 between the conduit 22 and the tube 47 and beyond the partition 51. The resonating chamber 42 also may be connected to the conduit 22 by acoustical coupling means 61 formed by the openings 55 associated with the llouvers 57 and extending throughout the greater part yof the sec-tion of the tube 22 enclosed within the resonating chamber 42.

The muiler 10 may be provided with an inlet coupling 62 and an outlet coupling 63 by which the structure may be connected in any suitable manner in the exhaust conduit of an internal combustion engine or other device where silencing of noises is desired.

In the present instance it is proposed to construct the resonating chambers and the acoustical couplings by which the resonating chambers are connected to the conduits 22 in such manner that the resonating charnbers may be tuned to a range of `sounds of different irequencies which may enter the structure through the inlet coupling thereof. For example, the resonating chamber 32 is a large chamber that may be tuned through the coupling 33 to relatively low frequency sounds emanating from the inlet conduit 21. The resonating chamber 39 is a smaller chamber which likewise may be tuned Ithrough the coupling 43 to somewhat higher frequency sounds emanating from the inlet conduit 21. The resonating chambers 41 and 42 are successively smaller chambers that may be tuned through the couplings 58 and 61 to successively higher frequency sounds within the conduit 22. The resonating chambers 52 and 53 likewise are successively smaller chambers that may be tuned through the acoustical couplings `54 and 56 to successively higher frequency sounds within the conduit 22.

The flow of fluid from the inlet conduit 22 is discharged into the inlet side 29 of the expansion chamber 28 from which the fluid flows to the outlet side 31 through the openings 24 in the partition 23. It will be apparent that the velocity of the uid in the conduit 21 decreases as it approaches the inner end of the conduit 21. Due to the size of the expansion chamber 28 Ithe tuid tlowing through the expansion chamber from the 20 nlet conduit 21 to the outlet conduit 22 will greatly decrease in velocity and increase in pressure. This provvides for a reversal of flow of fluid in the expansion ychamber 28 without creating excessive back pressure in the structure. The expansion of Huid in the expansion chamber 28 and the extensive and opposed walls by Awhich the expansion chamber is formed causes a con- :siiderable attenuation of sound in the expansion cham- E'ber by reflecting the sound waves.

It Will be apparent that the structure is relatively simple, compact and rigid and therefore relatively adaptable to low cost manufacturing and to the rugged service to which mufllers are normally subjected We claim: v V y 1. A muffler for an internal combustion engine coniprisin'g a tubular casing having end closures, said casing' having at least three internal transverse partitions, an imperforate inlet pipe extending from one end through an end closure yand through two of said partitions, and au exhaust pipe extending from the opposite end through the opposite end closure and two of said parti-tions, the middle partition having an opening therethrough for passage of gases, the partitions adjacent the middle partition each having an opening therein opposite the said inlet and exhaust pipes respectively.

2. A mufer for an internal combustion engine as set forth in claim 1, further comprising a third pipe concentrica'lly surrounding said exhaust pipe in radial spaced relationship, and a plurality of axially spaced Aannular partitions between rsaid exhaust pipe and said third pipe, said exhaust pipe having a plurality of openings on the circumference thereof between said annular partitions.

References Cited in the tile of this patent UNITED STATES PATENTS 1,021,254 Larkins Mar. 26, 1912 2,026,795 Oldberg 1an. 7, 1936 2,111,537 Noblitt et al. Mar. 15, 1938 2,116,751 Deremer May 10, 1938 2,138,477 Ludlow Nov. 29, 1938 2,151,470 Hollerith Mar. 21, 1939 2,182,204 Hector Dec. 5, 1939 2,191,620 Muller Feb. 27, 1940 2,520,756 Bryant Aug. 29, 1950 ,2,661,073 Deremer Dec. l, 1953 

